Docker

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Version

docker version
docker info

Network

• Docker uses docker0 virtual bridge interface. Each new container gets one interface automatically attached to the docker0 virtual bridge.
• Create network that other container will attach to and will be visible via name: docker network create -d bridge my-net (-d Network Driver: bridge)
• Attach container to custom network: docker run --network my-net ...

Socket Docker socket from within a container: -v /run/docker.sock:/run/docker.sock

Manage Docker as a non-root user The docker daemon binds to a Unix socket instead of a TCP port. By default that Unix socket is owned by the user root and other users can only access it using sudo. The docker daemon always runs as the root user.

If you don’t want to use sudo when you use the docker command, create a Unix group called docker and add users to it. When the docker daemon starts, it makes the ownership of the Unix socket read/writable by the docker group.

• Add the docker group if it doesn't already exist:

sudo groupadd docker

• Add the connected user "$USER" to the docker group. Change the user name to match your preferred user if you do not want to use your current user:

sudo gpasswd -a $USER docker

• Log out/in to activate the changes to groups.

• You can use docker run hello-world to check if you can run docker without sudo.

Dockerfile

Better way of installing things when building docker images:

RUN set -ex; \ # Fail when exit status not 0, print each command (debug)
	apt-get update; \
	apt-get install -y --no-install-recommends \

Tag, Build & Push

WARNING

The tag: latest can be missleading. Latest simply means "the last build/tag that ran without a specific tag/version specified".

Run docker build inside a directory containing single file called Dockerfile

Command	What it does
docker build -t Registry/Image:tag .	Build Docker image (-t with tag)
docker build -t registry/image:tag registry/image:another_tag .	Build image and use multiple tags
docker build -f Dockerfile_custom -t docker.mot-solutions.com/msi/sessionmanager .	Specify custom Dockerfile
docker push docker.mot-solutions.com/msi/sessionmanager	Push built image to registry
docker build --no-cache ...	Force Docker to clean rebuild every layer
docker tag 0e5574283393 fedora/httpd:version1.0	Tag an image referenced by ID
docker tag httpd fedora/httpd:version1.0	Tag an image referenced by Name
docker tag httpd:test fedora/httpd:version1.0.test	Tag an image referenced by Name and Tag

Run

docker run ...	Explained
-d	In background, detached
--name some-name	Use some-name for container Name
-ti	Interactive, with pseudo terminal
-p HOST:CONTAINER	Port mapping Ex. -p 8080:80
--rm	Remove after container stops
--privileged	Disable SELinux protection for this container
ctrl+p ctrl+q	Detach from container without stopping it
-v	Volume Mapping Ex. -v ${PWD}/config:/config
-v /run/docker.sock:/run/docker.sock	Map Docker socket
--network my-net	Use "my-net" network
--restart	Specify restart policy: no, on-failure, always, unless-stopped

Examples:

# RUN
docker run -d --name my_container -v $PWD:/directory image:tag # Detached (in background)
docker run -it image:tag bash # Run bash shell inside of a container
docker run -d alpine:latest sh -c 'while true; do date; sleep 1; done'
docker run -p 8080:80 --name -e VAR=Value my_container image:tag  # docker run -p 8080:80
docker run --restart=always redis

# COPY
docker cp foo.txt mycontainer:/foo.txt                        # Copy from host to container
docker cp mycontainer:/foo.txt foo.txt                        # Copy form container to host

Manage

Command	What it does
docker newtork ls	List Docker networks
docker volume ls	List Docker volumes
docker ps	Show running containers
docker ps -a	Show all containers (including stopped)
docker exec -it <my_container> bash	Attach to a running container with BASH shell
docker kill <my_container>	Kill running container
docker rm <my_container>	Remove the container (including data inside)
docker stats	Show Docker container system stats (CPU, Mem, IOs)
docker stats <my_container>	Show stats for a single container
docker logs <my_container>	Show logs from a container
docker inspect <my_container>	Return low-level information on Docker objects in JSON format
docker history <image>	Show the history of an image

System

Command	What it does
docker system df	Show Docker disk usage
docker system info	Display system-wide information
docker system prune	Remove unused data

Docker-Compose

User version 2 over version 3. The version 3 is used when using docker swarm and removes syntax used in version 2.

What it does	Command
Stand Up docker-compose.yml stack	docker-compose up -d
Restart single service from docker-compose.yml	docker-compose restart <service>
Add service to docker-compose.yml and start it	docker-compose up -d --no-recreate

Logs

Show last 100 logs from docker-compose deployment

docker-compose logs
-f            # Follow log output
-t            # Show timestamps
--tail="100"  # Number of lines to show from the end of the logs
              # for each container

Tips & Tricks

# ALIASES in .bashrc or .zshrc
alias dps='docker ps --format "table {{.Names}}\t{{.Image}}\t{{.Ports}}"'